Summary
This paper describes an example of drilling-hazard mitigation. It
demonstrates how a completely fresh approach, involving geomechanical analysis,
planning of a new revised well trajectory, and real-time well monitoring, can
reduce nonproductive time and cost and mitigate against unplanned terminal
events.
Recent drilling operations in a mature field in the North Sea were severely
disrupted by wellbore deterioration, stuck pipe, and lost-circulation
incidents. A complex geological sequence of tilted fault blocks and partially
depleted reservoir sands made well-trajectory and wellbore-stability planning
difficult. After two unsuccessful sidetrack attempts, an integrated
operator/contractor team performed a detailed audit of the drilling problems
and built a geomechanical Earth model to evaluate drilling hazards and develop
strategies to mitigate any further wellbore instability. Well objectives were
re-evaluated, and a new approach to the drilling process was developed. The key
was simplification of the well path. The operational solution featured
management of drilling hazards through a real-time risk-mitigation process.
Additional engineers at the wellsite managed drilling parameters; continuously
monitored cavings, cuttings, and drill fluids; and analyzed drilling mechanics
and logging-while-drilling (LWD) log data for indications of impending
problems. A Web-based real-time data-transfer system was used to deliver data
to the onshore drilling and subsurface teams. These methods, combined with
advanced communication techniques, enabled tight control of drilling parameters
and trajectory and enhanced collaborative understanding within the
multidisciplinary team. The third sidetrack was completed without incident,
within time, and under budget.
© 2005. Society of Petroleum Engineers
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History
- Original manuscript received:
7 June 2004
- Revised manuscript received:
14 June 2005
- Manuscript approved:
17 July 2005
- Version of record:
15 September 2005
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